Do You Need A Vapor Barrier Under Cement Board at jesseeesteveso blog

Do You Need A Vapor Barrier Under Cement Board.to qualify as a vapor barrier the perm rating has to be below 1.0 perms for residential use and below 0.5 perms for commercial use. You want exactly one vapor barrier layer on your wall.

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why vapor barriers are necessary.if you create enough thermal break than no barrier is needed. If you do not, then you need additional poly vapour barrier.

ALUTRIX 600 Vapour Barrier Rubber4Roofs

Do You Need A Vapor Barrier Under Cement Board So if you are using a surface applied. You should not place a vapor barrier behind the backer board. So if you are using a surface applied.to qualify as a vapor barrier the perm rating has to be below 1.0 perms for residential use and below 0.5 perms for commercial use.